For a game that's considered Microsoft's premier 360 title this holiday season, it's amazing how sloppy Mass Effect is. Graphical glitches distract from otherwise fascinating character designs and alien vistas, constant stops and stutters lengthen load times, and the inventory system must be the worst in history. And just as you're gnashing your teeth at this appalling lack of polish, you'll realize the light creeping through the blinds is the sun, you've played all night, and you're due at work in an hour.

Yep, Mass Effect is a game you'll hate to love. It boasts one of the best role-playing concepts ever, but trips itself up in execution at almost every turn.

The game is set in 2183, with humans having mastered interstellar travel only to discover they occupy a Gene Roddenberry-esque galaxy filled with alien species jockeying for political and military might. You control Commander Shepard, a figure who, naturally, ends up playing a crucial role in how the game's imminent galactic crisis pans out.

To say much more would spoil the story, as it truly is the game's brightest point — and also the best distraction from its blemishes. This is sci-fi pulp on an epic scale: The universe Mass Effect occupies — and which you can freely explore — is so richly detailed that an in-game encyclopedia is provided, with reams of information on every species, machine, cabal, and spacecraft you can encounter.

Much of your time is spent conversing with comrades and other beings you'll cross paths with, and the "role-playing" comes in how you choose to deal with them. Tense moments can be defused by careful negotiation or settled immediately with a laser bolt between the eyes. Likewise, chats with crew members can lead to anything from bloodshed to racy blue-skinned alien nooky that would make James Tiberius Kirk proud. It all depends on how sharp or silver your tongue is.

But for every highlight, there's something that distracts. Take the visuals: The game looks extraordinary, with creatures and costumes just as cool as anything you'll see in a sci-fi movie. But the textures and details always appear a few seconds late, so with every new scene, characters — even entire alien horizons — load before your eyes. Never mind the current competition; stuttering, clumsy graphics such as these weren't acceptable 10 years ago.

Most infuriating, though, is the game's inventory-management system. Exploring the galaxy nets you all sorts of high-tech weapons and fancy space duds — but bizarrely, there's no easy way to see what the hell you're carrying. No all-inclusive item list, no ability to sort anything, and some of your booty is virtually invisible unless you drill down through several layers of menus. Aggravating this is an arbitrary 150-item limit, practically nothing when skirmishes yield dozens of bits of loot you're automatically forced to pick up. You can't tell how close you are to hitting your limit, and when you do, your newest acquisitions are automatically discarded.

Lesser games have been killed for neglecting such fundamentals. Lucky for Mass Effect, it does enough right to survive its shortcomings . . . but only barely. RPG and sci-fi aficionados will scan each uncharted world and explore every morsel of dialogue, but less ardent gamers might be happier on good ol' terra firma.